High-Speed Traders Pulled Back, Not Out, After Fake Tweet

By

Jacob Bunge

April 24, 2013 4:15 p.m. ET

High-speed trading firms pulled back from the market during Tuesday's rapid, Twitter-fueled swoon, but they didn't pull out altogether, according to executives.

Automated trading programs dialed back exposure to stocks and futures and quoted less-aggressive prices as stock indexes fell in the wake of a bogus Twitter post claiming an attack on the White House, but trading systems and exchanges held up under the stress, traders...